1. Field of the Invention
The present invention relates to a screw, particularly to a screw with double notches.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional screw 1 comprises a head portion 11, a shank portion 12 extended outward from the head portion 11, a threaded section 13 spirally surrounded on the shank portion 12, and a cutting notch 14 defined on the shank portion 12. Wherein, a drilling portion 121 is formed on one end of the shank portion 12, opposite to the head portion 11. A drilling tip 1211 is further defined on a distal end of the drilling portion 121. The cutting notch 14 is defined on the shank portion 12 and extended toward the drilling portion 121. By imparting a drilling torque upon the head portion 11, the threaded section 13 is able to assist the screw 1 in drilling into an object 2. Herein, the cutting notch 14 preferably scrapes away and severs the wood fiber of the object 2 into debris to facilitate the removal of the debris, and the redundant debris without being removed out of the object 2 thence enters the cutting notch 14. Thereby, the screw 1 achieves a fixing ability.
However, the screw 1 has the following disadvantages:
1. The single cutting notch 14 is in fact unable to thoroughly sever the wood fiber of the object 2 tangling on the shank portion 12. Thus, the unsevered wood fiber adversely results in the increased drilling resistance. Moreover, the sole cutting notch 14 on the shank portion 12 cannot provide an adequate room for accommodating and timely extruding debris. Thus, the debris that is untimely extruded will block up the cutting notch 14, and the situation even becomes worse since the rest of the debris subsequently enters the constricted cutting notch 14. As a result, the crowded cutting notch 14 thence brings about a split object 2.
2. As aforementioned, the debris blocking up the constricted cutting notch 14 unbeneficially increases the drilling resistance and influences the drilling speed. Herein, if the object 2 is made of a material having the property of high density, more drilling torque imparted on the screw 1 is thence needed as a huge drilling resistance occurs on the blocked cutting notch 14. As a result, the construction on the cutting notch 14 might be abraded, and the shank portion 12 might be broken.